1. Field of the Invention
The present invention relates to a digital television broadcasting system, in particular to a digital television relay system which is capable of relaying a broadcasting signal discharged from a broadcasting station wirelessly.
2. Description of the Prior Art
A digital television broadcasting is being watched with keen interest in respect of providing a multimedia communication service to a subscriber. A terrestrial digital television transmission method can be divided into a COFDM (Coded Orthogonal Frequency Division Multiplexing) transmission method based on a DVBT (Digital Video Broadcasting-Terrestrial) standard of Europe and a 8 VSB (Vestigial Side Band) transmission method based on an ATSC (Advanced Television System Committee) standard of North-America.
The digital television broadcasting in accordance with the ATSC standard is transmitted with a MPEG2-TS (Moving Picture Expert Group 2-Transport Stream) format, accordingly it is possible to multiply video and audio data and transmit it through a high speed channel, and it is also possible to perform an interactive data service besides the digital television broadcasting. In addition, the digital television broadcasting method adapts a 8 VSB modulation method using 6 MHz bandwidth, accordingly it is possible to provide a multimedia service combining broadcasting and communication even in SDTV (Standard Definition Television) circumstances when a STB (Set Top Box) is connected to a television set adapting a NTSC (National Television Standard Committee) method which is the present analog broadcasting standard.
In order to perform above-described television broadcasting services smoothly, development of a digital television relay system for relaying a certain quality broadcasting signal to subscribers in radio shadow areas is essentially required.
In other words, subscribers in the radio shadow areas such as a place under a high building or in shadow areas such as a remote place can not receive a broadcasting signal transmitted from a broadcasting station as a high quality. In this case, increasing output of the broadcasting station is difficult to realize because of high expenses and frequency legislation. Accordingly, the digital television relay system which is capable of transmitting a broadcasting signal after making a week broadcasting signal into a strong signal is required in order to provide the service to the shadow areas with low expenses.
In order to solve above-mentioned problems, the object of the present invention is to provide a digital television relay system which is capable of providing a digital television broadcasting service with a transmission quality same with a broadcasting station to a subscriber in shadow areas by compensating a transmission error occurred in space after receiving and channel-decoding a broadcasting signal transmitted from the digital television broadcasting station and channel-coding it again.
The digital television relay system according to the present invention comprises a front end unit for transmitting/receiving a certain broadcasting channel frequency signal, a VSB demodulator unit for converting the certain broadcasting channel frequency signal received from the front end unit into intermediate frequency and performing channel decoding with a VSB method, a VSB modulator unit for compensating a transmission error occurred on space about the signal channel-decoded on the VSB demodulator unit, an exciter unit for up-converting the signal outputted from the VSB modulator unit into a transmission channel frequency allotted so as to be different from a reception channel frequency, a power amplifying unit for amplifying power of the signal up-converted on the exciter unit, a VSB corrector unit for yielding a compensation value in order to compensate a non-linear error of the signal outputted from the power amplifying unit and providing it to the VSB modulator unit, and a control unit for performing overall control of the digital television relay system.